Build your Mini Cairns.

How this fits in the OS.

What you'll build.

A vault folder on your computer with the Cairns three-tier skeleton in it, an agent contract at the root, day-one personal waypoint files already seeded, and three skills installed that drive the loop from here on. The whole thing is markdown. No database. No server. No accounts to create.

Be honest about what this is. It is a student-scale demo, not the production Cairns. The production version has a full Librarian service, vector search (a way for the agent to find similar text without exact keyword matches), graph storage, and multi-agent routing. Yours has none of that. That is fine. You are not building the system. You are learning the shape so the production version makes sense when you add layers later.

What changes for you.

The folders are the easy part. The bigger thing is how you start treating capture, recall, and standing context. Three internal shifts you should expect to feel in the first two weeks:

• You stop opening a blank chat to think. The waypoint files become the place you check first when you sit down. The agent's working memory loads from them before you say a word, so the conversation starts already grounded in your active projects, your people, and your open decisions.
• You start trusting that yesterday is still there. Raw evidence is preserved at L3 before any summary runs. Dense cards at L2 Chain of Density Card Catalog Layer point back to the raw. Six months from now, when you want to know what was actually said in a call this Tuesday, the verbatim is on disk where the agent can read it.
• You stop hoarding folders for every interesting thing. Five L1 categories is a cap, not a target. The discipline forces you to choose, and the choosing is the value. Most things do not need to live in your standing memory.

Two weeks in, the vault is right more often than wrong. That is the moment the second brain becomes load-bearing instead of decorative.

Before you start.

The build.

Six steps. Folders first, day-one waypoints next, skills last, then a smoke-test capture and a lint pass. Each step has a duration and a recovery line. The skills do most of the writing; your job is to pick categories that match your life and approve what the agent proposes.

The agent contract.

Every Mini Cairns vault ships with an AGENTS.md file at the root. Any agent that opens the folder reads this contract before doing anything else. It is short, it is load-bearing, and the whole architecture rests on the third section.

When it works.

You will know the vault is real when these five things hold after one week of light use:

1. The folder skeleton matches the map above. L1, L2 Chain of Density Card Catalog Layer, L3, day-one waypoints, AGENTS.md at the root, three Cairns skills installed.
2. Your five L1 files have honest content in them. Not empty, not padded. One to three real lines per active item. Updated when something resolved.
3. You ran /cairns-ingest on a real source at least once. The L3 raw is verbatim. The L2 Chain of Density Card Catalog Layer card is dense and cites the L3 path. The L1 layer either got a proposed waypoint you approved or it stayed unchanged on purpose.
4. You can open a fresh Claude Code session in the vault folder, ask "what am I shipping this week?", and the agent answers from your L1 waypoints without you restating context. That is the compounding test. The agent's working memory loaded from the vault.
5. The end-of-day ritual takes you three minutes. Open decisions-in-flight.md first, then work-builds.md, update or close what resolved, done. If it takes longer, the L1 files have drifted long and lint will tell you next pass.

Hit all five and the vault is doing its job. Two weeks of that and you stop wondering whether the second brain is worth keeping.

If you get stuck.

Common failure modes, ranked by how often they bite people on the first build:

• You picked sixteen categories instead of five. Most common first-time mistake. The cap is the discipline. Cut back to five. Add a sixth or seventh only when you find yourself force-fitting items into the existing five for a week running.
• Your L1 files are empty. Empty waypoints are invisible to the agent. One real line per active item, written today, beats a perfect structure with nothing in it.
• The skill cannot find your vault. The vault path was ambiguous and the skill guessed wrong. Tell the agent explicitly: "the vault root is <your path>, use that for every Cairns skill from now on." Save that in your CLAUDE.md so future sessions inherit it.
• An L1 file got updated without your approval. The contract was violated. Stop. Open the AGENTS.md at the vault root and re-read the Human Approval Gate section to the agent. Confirm the rule before continuing. If it keeps happening, the skill spec drifted and needs to be reinstalled from templates/obsidian-cairns-starter/.
• You are ingesting more than ten sources a day. You are ready to graduate from manual /cairns-ingest runs to a real Flow capture pipeline. The Mini Cairns shape was built for hand-driven capture. Crossing ten a day is the signal to add an ingest daemon.
• You are ingesting less than five sources a week. Your categories are probably wrong for your actual life. Re-pick. Five categories that match the work you are doing this month, not the work you wish you were doing.

Still stuck? Post the prompt, the agent's response, and what you expected, in the workshop Slack. Someone in the cohort is solving the same thing.

Where to go next.

You have the vault. The skills are wired. The contract is in place. The compounding starts when you keep using it. The natural next moves on the shelf: